In the past, various means such as massage, acupuncture and sleeping have been adopted to relax the brain state or to increase the power of concentration. (This technique will be referred to “the prior art 1” later.)
Patent document 1 discloses a method of measuring changed concentrations in oxyhemoglobin and deoxyhemoglobin using the near-infrared spectroscopy before an external stimulus to be evaluated is applied to a test subject and after it has been applied to the same test subject, then hearing the subjective amenity from the test subject when said external stimulus is applied thereto, and estimating the appropriateness of the external stimulus to the human body based on the measurements and the subjective amenity.
The near-infrared spectroscopy means a method of irradiating a brain with a feeble near-infrared light (e.g., 680-1300 nanometers) through the skull and scalp of a human body and measuring the changed concentrations of oxyhemoglobin (Oxy-H b; HbO2) and deoxyhemoglobin (Deoxy-Hb; Hb) in the blood in the brain surface immediately inside the brain (cerebral cortex). (This method will be referred to “the prior art 2” later.)